As the development of biometric devices for identity verification, and in particular of fingerprint sensing devices, has lead to devices which are made smaller, cheaper and more energy efficient, the possible applications for such devices are increasing.
In particular fingerprint sensing has been adopted more and more in, for example, consumer electronic devices, due to small form factor, relatively beneficial cost/performance factor and high user acceptance.
Capacitive fingerprint sensing devices built based on CMOS technology for providing the fingerprint sensing elements and auxiliary logic circuitry are increasingly popular as such sensing devices can be made both small and energy efficient while being able to identify a fingerprint with high accuracy. Thereby, capacitive fingerprint sensors are advantageously used for consumer electronics, such as portable computers, tablet computers and mobile phones, e.g. smartphones.
Manufacturing an electronic device often involves assembling a large number of components which have been manufactured elsewhere. It is customary to verify the functionality of each component after it has been produced. However, there is also a need to verify the functionality of individual components in the electronic device after the device has been fully assembled to ensure that the end user receives a fully functional device.
In particular, it is desirable to test the fingerprint sensor so that it is working as expected and that it captures images of sufficiently high quality. Since it is not practical to test the fingerprint sensor with an actual finger, a test rig can be used which comprises a rubber stamp or a rubber probe having a pattern allowing the functionality of the fingerprint sensor to be verified.
However, such a rubber stamp may become worn which can lead to a degradation of the acquired test image, or at least to inconsistencies in the measurements since the pattern will wear and thus not stay the same when used for a large number of measurements. Moreover, arranging a rubber stamp or probe in contact with the sensor requires a dedicated machine setup to mechanically position the test pattern on the fingerprint sensor, thereby making the overall assembly process more complicated.
Accordingly, it is desirable to simplify testing of a fingerprint sensor in an electronic device.